Zn1-xNixO (x=0, 0.5) nanoparticles were successfully prepared by sol gel method. Structural analysis was performed by XRD confirming phase purity and crystalline wurtzite structure. Surface morphology of nanosystems was performed by Scanning Electron Microscopy (SEM) and High Resolution Transmission Emission Microscopy (TEM) .Due to doping of ZnO nanoparticles the absorption shifted towards the visible region from UV region .The absorption increases on doping in the visible region.The Photocatalytic activity of both the doped and undoped ZnO was analysed via degradation of Methylene Blue. The Methylene Blue decomposition rate of pure ZnO and Nickel doped ZnO nanoparticles were studied under UV –Visible region. In the visible region both pure and doped ZnO decomposed Methylene Blue.This confirms the potential application of ZnO Nanoparticles for removal of harmful dyes from waste water and drinking water.The doping has a pronounced effect on the photocatalytic activity of nanoparticles. The degradation rate of the dye increased in case of Ni doped ZnO nanospheres.